The present invention pertains to a cutting tool such as, for example, a milling insert or a cutting insert, comprising a flank face, a rake face, and a cutting edge at the intersection of the flank and rake faces, for chip form machining of workpiece materials. In the case of a milling insert, such a cutting tool has been typically used to mill workpiece materials. In the case of a cutting insert, such a cutting tool has been used to chip form machine workpiece materials.
For the most part when made from a cermet, cutting tools are comprised of tungsten carbide cermets (WC-cermets), also known as cobalt cemented tungsten carbide and WC-Co. Here, a cobalt binder (Co-binder) cements tungsten carbide particles together. Although WC-cermets have achieved successful results as a cutting tool, there are some drawbacks.
One drawback is that up to about 45 percent of the world's primary cobalt production is located in politically unstable regions (e.g., political regions that have experienced either armed or peaceful revolutions in the past decade and could still experience additional revolutions). About 15 percent of the world's annual primary cobalt market is used in the manufacture of hard materials including WC-cermets. About 26 percent of the world's annual primary cobalt market is used in the manufacture of superalloys developed for advanced aircraft turbine engines--a factor contributing to cobalt being designated a strategic material. These factors not only contribute to the high cost of cobalt but also explain cobalt's erratic cost fluctuations. Consequently, cobalt has been relatively expensive, which, in turn, has raised the cost of WC-cermet inserts which in turn has raised the cost of cutting tools. Such an increase in the cost of cutting tools has been an undesirable consequence of the use a Co-binder for WC-cermet inserts. Therefore, it would be desirable to reduce cobalt from the binder of cermets.
Furthermore, because of the principal locations of the largest cobalt reserves, there remains the potential that the supply of cobalt could be interrupted due to any one of a number of causes. The unavailability of cobalt would, of course, be an undesirable occurrence.
Cutting inserts may operate in environments that are corrosive. While WC-cermets having a Co-binder have been adequate in such corrosive environments, the development of a cutting tool that has improved corrosion resistance without losing any of the chip form machining performance remains an objective.
While the use of WC-cermets having a Co-binder for cutting tools has been successful, there remains a need to provide a material that does not have the drawbacks, i.e., cost and the potential for unavailability, inherent with the use of cobalt set forth above. There also remains a need to develop a cutting tool for use in corrosive environments that possess improved corrosion resistance without losing any of the cutting performance characteristics of cutting inserts made of WC-cermets having a Co-binder.